Manufacture of calcium carbid.



i dust.

the carbid-forming reaction,

' to adapt them an s rs earner nro FREDERICK M. BECKET, OF NIAGARA FALLS, NEW YORIL ASSIGNOR TO UNION CARBIDE COMPANY, OF NEW YORK, N. Y.,

I MANUFACTURE OF CALCIUM CARBID.

No Drawing.

To all whom/it may concern Be it known that I, FREDERICK M. Brewer,

ments in the This invention relates to the manufacture of calcium carbid, and particularly to an im- "proved process of preparing the charge for reduction in the electric furnace.

It has heretofore been customary in this art to smelt a loose mixture of lime and carbon,in more or less finely-divided condition; and also to briquet mixtures of this kind in order to allow a more ready escape of the reaction gases and to avoid the formation of In such briqueting processes, the lime is :usually mixed with coke, charcoal, anthracite or other form of fixed carbon in substantially the proportions require together with the minimum necessary proportion of a suitable binder, usually a hydrocarbon or a carb'ohydrate. The briquets are formed under high pressure, baked if necessary to increase their strength, and smelted down in an electric furnace. Such briqueting processes are of course highly expensive.

According to the present invention, the charge is agglomerated strong aggregates (that is to say, aggregates which are sufficiently resistant to crushing for use in the largest furnaces), without resorting to briqueting or molding operations of any kind. The aggregates shape and size, but have proven excellently adapted for furnacing, yielding a commercial grade of carbid, affording an excellent distribution of the reaction gases, and a nearly dustless operation.

An example of the invention is as follows: Galcined limestone is mixed directly with a definite proportion of 'a suitablebituminous coal rich in volatile matter, and the mixture is subjected to a cokingbperation, preferably in coke ovens of the so-called by-product type. In order, under these conditions,

to obtain aggregates suitable for furnacing,

' ithas been found necessary that certain definite conditions should be observed. In

Specification of Letters Patent.

Application filed January 20, 1915.

Manufacture of Calcium Qarbid, of which the following is a specification.

for

into mechanically formed are usually irregular in burned lime in the proportion of 110 parts being collectedas in the usual cokin tity for this purpose.

A CORPORATION OF VIRGINIA.

Serial No. 3,384.

the first place, the quantity of carbon 1remaining in association with the lime after the coking operation should be substantially f that required for the carbid-forming reaction oao+eo=cac,+oo. In the second place, the quantity and nature of the bituminous matter which-was as-.

sociated in the original coal with the abovespecified quantity of fixed carbon, must be such as to yield, without the necessity of heavy pressures, the mechanically strong aggregates above described. It will be understood therefore that coal having a rather definite character and composition must be used, although some variation from a fixed standard is permissible. In practice, I have been able to obtain excellent results with grades of bituminous coal containing from about 30 percent. to about 36 per cent; of volatile hydrocarbons. It maybe practica ble to employ coals containing a somewhat lower percentage of volatile hydrocarbons, say from 26 percent. upward. In the practice of the process, I have. successfully used a coal from the Youghiogheny district in Pennsylvania, which contained, after drying Volatile matter 35. 84% Fixed carbon 53. 7 7 Ash 10.39%

Total 100.00%

Moisture as received 1. 60%

The above coal was mixed with freshly of coal to 100 parts of lime, and the mixturewas coked in by-product coke ovens of the regular type, the gas, tar, and ammonia process. The evolved gas was burned 'or the coking and proved to be suiiicient in quan- After coking, the resulting mass is crushed to lumps, which may be about the size'of thefist or larger, and

these lumps are preferably conveyed while still hot to the electric furnace. The aggregates thus prepared are mechanically strong,

and will endure considerable weathering without material injury, although the coked Patented Apr. 2?, was.

a one-eighth inch mesh,

. as in ordinary coking,

sh, Lu

mass cannot be fully quenched withwater,

as it would thendisintegrate. it is found that the aggregates are somewhat stronger if the coking is so conducted as to-leave some three to four per cent. of volatile matter, but they usually possess suliicient strength even after the volatile matters have been expelled with substantial completeness.

In preparing the mixture for coking it is preferred to grind the lime and coal to pass and it is desirable that the groundmaterial tim-ately mixed. Gears-er ground materials, say one-fourth inch and larger, donut form an equally strong aggregate. which is very rich in bituminous matter is available, it is in some cases possible or ticable to add to the charge before coking, arelatively small proportion of carbonaceous matter,'such as coke, or anthracite, which is high in fixed carbon, andlow in bituminous matters. It would also be possible, in case the bituminous coal were too poor in bi: tuminous matter to yield aggregates of the necessary strength and resistance to crush ing, to add relatively small quantities of another binder, usually bituminous in charac-' ter. ever never necessary in practice, since satisfactory grades of coal are easily obtained It will be observed that in accordance with the present invention, the bituminous coal serves as the principal or predominating source of supply for both the fixedcarbon and the coking binder.

The present process is distinctively ad- I vantageous as applied to the production of calcium carbid as distinguished from other reduction processes. This is primarily due to the relatively very high proportion of fixed carbon which is necessary for the carbid-forming reaction, "as compared with processes for the reduction of metals. Thus the react10nzrequires a proportion of fixed carbon equal to about tlsq per cent. of the lime used, whereas the reaction involved in'the reduction of silica requires a quantity of fixed carbon amounting only to about 40 per cent. of the silica. Similarly in the reduction of iron ozrid according to the equationshould be very in- Tn case coal prac- Such bituminous additions are how:

' coking conditions,

with thelixed carbon bituminous coal," a

foundto have a decidedly ni htwear-i n resistance, under the furnacingconditions, than the ordinary mixtures of-liunp lime and lump coke; from which it follows that more deeply buried in the charge, thereby conserving a large amount ofvheat; or if desired, higher voltages may be successfully employed in the furnace, which is a very material advantage, especially in the case of large furnaces, as the higher voltage gives a higher power factor; This also means that process may be mentioned the fol-- with a given voltage the electrodes may be the presentmixturepermits the use, (with a given power factor) of larger furnaces than could otherwise be employed. There is also the advantage of at a higher frequency on a vfactor,

a given decided with th quets,

given power or of improving the power factor at frequency. --The foregoing are very e use of compressed or molded brithe conductivity of'which is rela- .tivelyhigh. The process is also advanta geous in that it secures all the advantages of intimate mixing, with the resulting higher ,fyields, and lessened wear on the electrodes, without the disadvantage of using :a powdered mixture inthe furnace. The method is furthermore economical, inasmuch as the coking is carried out under standard methof volume than is necessary for the coking of the coal alone. i I I I claim V i. In the manufacture of calcium carhid, the process of preparing aggregates suitable for furnacing, which consists in mixing lime and-a suitable coking coal in such proportions that the fixed carbon of the coal will substantially suffice for the carbid-forming reaction, said coal being suficiently rich in bitunn'nous matter to yield with the lime, in the proportions stated and under ordinary a mechanically strong ag regate suitable for furnacing, and then coking said mixture.

2. Tn the manufacture of calcium carbid, the process of preparing aggregates suitable for furnacing, which consists in mixing lime and a suitable coking coal containing nitrogen in such proportions that the fixed carbon of the coal will substantially suffice for the carbid-forming reaction, said coal being sufliciently rich in bituminous matter to yield with the lime, in the proportions stated and under ordinary coking conditions, a

mechanically strongaggregate suitable for practical advantages as compared,

ods, and requires even less time per unit memes?" g,

furnacing, and then coking said mixture in conditions, a mechanically strong aggregate a by-product oven and collecting the volatile suitable for furnacing, coking said mixture, products, including ammonia. and thereafter embedding electrodes within 3. The process of making calcium carbid, a charge of said mixture and smelting said which consists in mlXlIlg lime'and a suitable charge to produce calcium carbid.

coking coal in such proportions that; the In testimony whereof I alfix my signature fixed carbon of the coal will substantially in presence of two witnesses.

' sufiice for the carbid forming reaction, said FREDERICK M. BECKET.

coal being sufliciently rich m bituminous Witnesses; matter to yield with the lime, in the pro- F. B. MORGAN,

- portions stated'and under or 'nary coking D. Bunsnss. 

